# What does it mean to have a fixed lense aperture with variable camera aperture? [duplicate]

I recently ordered the Nikon Z 24-120mm f4S and one of the features every reviewer sort of mentioned is its fixed f4 aperture. What I (a novice) wants to really understand is how does this affect my photos when I can set a different aperture in the camera and yet the lense has a fixed aperture - so when I set f5.6 on Aperture Priority mode - does nothing really happen? I am confused - please help me understand.

Thanks!

The focal length of a lens establishes the magnification (image size of objects) and angle-of-view), wide-angle, normal, or telephoto. With a zoom lens mounted, you choose the realm that best suits your needs for each shot. The f-number relates to how much light the lens will gather. Lenses can be thought of as light funnels, the larger the working diameter (aperture width) the more light the lens will collect. A setting of f/4 means the lens can image in subdued light conditions.

You need to know; the f-number value is mathematically calculated by dividing the working aperture diameter into the focal length. As an example, if the lens is set to focal length 50mm and the aperture diameter is set to 12.5mm, then the lens is functioning at f/4.

Now the fact that this is zoom lens complicates the f-number concept. Consider that as you zoom, you are changing the focal length and this action would normally change the f-number (derived by dividing working diameter into working focal length), The quality zoom lens has a trick up its sleeve, it is able to keep the f-number the same (constant) as you zoom. This is no small feat! Most zooms cannot, instead, they give up as the zoom approaches the upper limits of its telephoto range. Yours sports a constant f/4 if this is your setting, throughout the zoom.

How this works, yours is a “high-end” zoom (good stuff), it keeps a constant f-number. This lens has a front lens element group that acts like a magnifier. This shows the outside world a view of the aperture (iris diaphragm) that seems to change its diameter as you zoom. The key here, the irs appears to expand and or shrink as you zoom. This is clever, it keeps the f-number constant.

What the words. “Constant f/4” means. When this lens is set to a large aperture like on near maximum like f/4 (or any other f-number setting), this lens will maintain this setting as you zoom.

What is meant by fixed aperture is that the maximum aperture does not change when the focal length changes... i.e. it is not a variable aperture zoom lens like the 24-200 f/4-6.3 is.

The aperture does change based upon the aperture set by the camera.